I see your point. Probably this has to do with level. My guess would be that at the levels I am working, I don't have to worry about anyone checking the book, since they don't usally even have one. I would guess that at the higher levels, coaches are more "detail-oriented" and more likely to check these things up. But I still think that if I was off by only one number (such as 4-35 instead of 4-34) and I got the spirit and intent correct, it wouldn't be a huge deal against me. And if a coach did want to argue about the number, I could easily say, "But I DID get the rule right" and there would be one more coach who would have read the rule book, and seen the interpretation there on the floor. But perhaps I am wrong about this at the higher levels.
Juulie--
I am not sure it has anything to do with levels of ball. 95%+ of the times you used this you could easily get away with saying
any rule you wanted to because the coach would never look it up (might not even have a rule book), but if one coach called you on it and you were wrong, your credibility will suffer big time. I guess you have to ask yourself if it a risk you are willing to take. I, for one, am not willing to risk it.
I have told coaches many times what a rule states and they have disagreed with me, so after the game I make a copy of the rule out of the book and fax it to them or e-mail them with a rule link (NCAA only). This method has never failed me because they are reading it for themselves with the rule reference right there. I don't do this all of the time and I generally tell the coach that I will send them the rule so they know it is coming.
Take all of this for what it is worth (not much

) and good luck with the coaches.